Posters

Modulation of the axis of total astigmatism of the cornea resulting from vector analysis of corneal front and back surfaces before and after routine cataract surgery

Poster Details

First Author: S.Patel UK

Co Author(s):    L. Tutchenko   O. Voytsekhivskyy   M. Skovron   O. Horak           

Abstract Details

Purpose:

To determine if any change in the axis of the total astigmatism of the cornea was influenced by the axis of the total astigmatism prior to surgery in routine unremarkable phaco in cases of clears corneas free significant irregularities.

Setting:

Department of Ophthalmology, Shupyk National Medical Academy of Postgraduate Education, Kyiv, Ukraine; Kyiv City Clinical Ophthalmological Hospital “Eye Microsurgery Center”, Ukraine.

Methods:

Astigmatism of both corneal surfaces (109 cases,one eye/patient), in the central 3 and 5mm optical zones, was measured using Orbscan II (Bausch&Lomb) before and after surgery at 1,2 & 3 months. The findings were evaluated by vector analysis to determine the astigmatic axis of the total cornea before and after surgery in each case. Surgery was standard routine phaco under topical anaesthesia (2.2 mm incision at 12o’clock, subconjunctival injection of dexamethasone and parabulbar injection of betamethasone. Postop topical levofloxacin, oftan-dexamethason, indomethacin, dexpanthenol, trehalose and hyaluronic acid. Only one type of spherical IOL was implanted in all cases.

Results:

Reporting major significant findings(p<0.05). For the axis of the minus cylinder over the central 3mm optical zone, change in the axis (°) of total corneal astigmatism (y) was related to axis of total corneal surface astigmatism before surgery (x) and for posterior corneal surface astigmatism (y1) and axis of posterior corneal surface astigmatism before surgery (x1). Linear regression revealed 1month(n=92), y=0.913x-0.005x2+3.049(r=0.505), y1=0.458x1-0.003x12+10.419(r=0.225). 2months(n=83), y=1.129x-0.006x2-1.813(r=0.755), y1=1.122x1-0.006x12-1.959(r=0.736). 3months (n=49), y=1.391x-0.008x2-0.701(r=0.635), y1=1.117x1-0.006x12+2.035(r= 0.582). For the anterior surface over this zone, change in the axis of astigmatism (y2) was related to preop axis (x2) at 1month only, where y2=0.003x22-0.449x2+37.91(r= 0.352).

Conclusions:

The change in the axis of total, and posterior surface, astigmatism of the cornea after phaco has a quasi-hyperbolic relationship with the axis before surgery. The results predict, by 3months postop there is little change in the axis when preop astigmatism is predominantly ‘with-the-rule’. However, substantial changes in excess of 50° are likely when preop astigmatism is predominantly ‘against-the-rule’.

Financial Disclosure:

None